Table 2. Details of SAXS data collection and analysis.

	PmScsCΔN	PmScsC	PmScsCΔLinker
SASBDB ID	SASDEK4	SASDER4	SASDEQ4
Data-collection parameters
Instrument	SAXS/WAXS, Australian Synchrotron
Beam geometry	Point
Wavelength (Å)	1.033
Sample-to-detector distance (m)	3.330
q-range (Å−1)	0.008–0.363
Temperature (K)	283
Absolute intensity calibration	Water
Exposure time (s)	38 (38 × 1 s exposures)
Configuration	Concentration series from 96-well plate
Protein concentration range (mg ml−1)	0.1–10.0
Sample details
Extinction coefficient [A 280, 0.1%(w/v)]	0.643	0.528	0.558
Partial specific volume (cm3 g−1)	0.742	0.741	0.743
Contrast, Δρ (1010 cm−2)	2.79	2.80	2.78
Molecular mass (from sequence) (kDa)	20.2	24.8	23.4
Protein concentration (mg ml−1)	0.50†	0.1, 0.5, 2.0, 5.0, 10.0	0.1, 0.5, 2.0, 5.0, 10.0
Structural parameters
I(0) (from Guinier) (cm−1)	0.004055 ± 0.00001	—	—
R g (from Guinier) (Å)	17.0 ± 0.1	—	—
I(0) [from p(r)] (cm−1)	0.004053 ± 0.00001	—	—
R g [from p(r)] (Å)	17.0 ± 0.1	—	—
D max (Å)	55 ± 2	—	—
Porod volume (Å3)	22200 ± 1000	—	—
Molecular-mass determination
Molecular mass [from I(0)] (kDa)	11 ± 2	—	—
Molecular mass (from Porod) (kDa)	19 ± 1	—	—

^†PmScsCΔN: I(0) = 0.00140 ± 0.00002 cm⁻¹, R _g = 16.9 ± 0.3 Å, M = 19.8 kDa (0.1 mg ml⁻¹); I(0) = 0.004053 ± 0.000001 cm⁻¹, R _g = 17.0 ± 0.1 Å, M = 19.1 kDa (0.5 mg ml⁻¹); I(0) = 0.01839 ± 0.00003 cm⁻¹, R _g = 17.1 ± 0.1 Å, M = 19.3 kDa (2.0 mg ml⁻¹); I(0) = 0.05463 ± 0.00005 cm⁻¹, R _g = 17.2 ± 0.1 Å, M = 19.6 kDa (5.0 mg ml⁻¹); I(0) = 0.10756 ± 0.00005 cm⁻¹, R _g = 17.0 ± 0.1 Å, M = 19.2 kDa (10.0 mg ml⁻¹). Masses from the Porod volume are used as concentration estimates, yielding masses from I(0) inconsistent with the expected mass. The 0.5 mg ml⁻¹ data were used for subsequent data analysis.